I have an ITA SCCA 91LS Integra (OBD0). I just got a 92LS (OBD1 engine and ECU (PR4) which I would like to drop in. Do I need to replace all the wire harnesses (ie, engine, interior, etc...) or can I just replace the Engine wire harness?

 

you can put the motor is and use your obd0 ecu, but if you want to convert to odb1 you will need only a conversion harness, obd1 ecu and a 4-wire o2 sensor

 

Thanks.